1. Field of the Invention
The present invention relates to an image process method, and more particularly, to an apparatus and image process method for enlarging and enhancing images.
2. Description of the Prior Art
It is common in the field of digital image processing to increase the resolution of a digital image in order to enlarge the image for display or hardcopy output. For example, when an HDTV receives television signals in NTSC format, since the image resolution provided by HDTV can go up to 1920 by 1080 while the image resolution in NTSC format can only be 648 by 486, it is necessary to perform image enlargement for displaying the images on the television.
Furthermore, sources images such as JPEG photographs, Internet, and WEBTV files are often compressed to reduce the storage capacity requirements. Therefore, when, for instance, a user would like to create a print of the file with higher resolution or merely to get a closer look at a particular detail within the original image, there will be a need to perform image enlargement.
Resolution enhancement is crucial to image enlargement, and it can often be done by interpolating the low resolution data to a higher resolution. In the image processing software of today, some of the computerized methods used for improving the data resolution include Sinc interpolation, bilinear interpolation, bicubic interpolation, and nearest neighbor interpolation. For each type of interpolation, a kernel function is used to compute the values of the new pixels based on the values of the original pixels sampled from the original image. Since the kernel functions used by interpolation methods are different from one another, each interpolation method will produce different results when enlarging the source image.
The methods mentioned above usually perform satisfactorily for interpolating images having smooth textures. However, as for some methods such as bilinear interpolation, the algorithms used tend to average image data across high-contrast boundaries like edges and rapid contrast change zones, which may cause a blocky or blurry result appears on the enlarged image. Hence, these methods are not effective in terms of edge and detail rendition.